Mechanical pencil

ABSTRACT

A mechanical pencil includes an outer casing and an inner casing. The inner casing comprises a lower plane on the same level has a lead protruding passage and teeth-shaped continuous notches opposed to the lower plane and forming a space between them. An S-shaped plate spring is engaged at its rear end in the notches and holds a lead at its front end portion. The spring is moved back and forth by means of a block loosely secured to it. An ear of the block projects outside of the outer casing so that the block may be moved by the thumb of the hand holding the mechanical pencil.

United States Patent Inventor Yukio llorie Tokyo, Japan Appl. No. 797,821 Filed Feb. 10, 1969 Patented Apr. 20, 1971 Assignee Dai Nihon Bungu Kabushiki Kaisha Tokyo, Japan (also trading as The Japan Stationery Co., d) qkyeJap Priority Feb. 14, 1968 Japan 43/ 10165 MECHANICAL PENCIL 3 Chins, 4 Drawing Figs. US. Cl. 401/83, 401/84 Int. Cl. 843k 21/18 Fieldoiseardi 401/84, 83, 66, 80

Primary Examiner-Lawrence Charles Attorney-Eliot S. Gerber ABSTRACT: A mechanical pencil includes an outer casing and an inner casing. The inner casing comprises a lower plane on the same level has a lead protruding passage and teethshaped continuous notches opposed to the lower plane and forming a space between them. An S-shaped plate spring is engaged at its rear end in the notches and holds a lead at its front end portion. The spring is moved back and forth by means of a block loosely secured to it. An ear of the block projects outside of the outer casing so that the block may be moved by the thumb of the hand holding the mechanical pencil.

MECHANICAL PENCIL This invention relates to a mechanical pencil.

The conventional push-type mechanical pencil, in which a lead is protruded by pushing the top of a holder, and a conventional screw-type mechanical pencil, in which a lead is propelled by a screw, are relatively intricate in construction. Such mechanical pencils often fail and are far more expensive than an ordinary lead pencil. Moreover, these conventional mechanical pencils require pushing on the top or rotation of a part whenever the length of the lead, protruding outside of the holder, is to be arranged. Therefore, these mechanical pencils are not suitable for the use of a soft lead, which wears out easily. Such pencils are particularly inconvenient to take down shorthand continuously for a long period.

An objective of the present invention is to provide an extremely inexpensive mechanical pencil of very simple construction and operation having a good writing touch.

A further objective of the present invention is to provide a mechanical pencil in which the length of the lead, to be protnrded outside of the holder, is arranged by the thumb of the hand holding the mechanical pencil during writing.

According to the present invention, an elongated casing is tapered and mounted by a conical cap at its fore end. The cap, which may be integral with the casing, has a passage through which a lead is protruded from the tip thereof. A space is formed, inside the casing, between a lower plane arranged on the same level as the lower surface of the passage and an upper plane opposite the lower plane and parallel to it. The upper plane has teeth-shaped continuous notches. An elongated split, lengthwise on the casing, communicates the exterior of the casing with the space. A U-shaped movable block is loosely secured within the space by means of a generally S-shaped plate spring. An ear integral with the block projects outside of the case through the split. The rear end of the S-shaped plate spring is engaged with the teeth-shaped notches and the fore end portion of the spring holds one end portion of the lead and presses it down against the lower plane.

When a user holds the mechanical pencil, according to this invention, in a manner to write, as the ear is located below the thumb of the user, he can push the ear forwardly along the split without changing the pencil in his hand. When the ear is moved, the rear end of the S-shaped plate spring engaging with the teeth-shaped notches advances within the notches one by one, so that the lead is protruded outside of the casing as long as the notches continue.

On the other hand, the ear can be pulled back, by the thumb, along the split when the mechanical pencil is being held during writing. When the lower edge of the rear end face of the U-shaped movable block pushes the lower curved portion of the rear portion of the plate spring, so that the spring is lowered and unfastened with its engagement with the notch, the ear is free to move rearwardly. Therefore, the lead is backed up smoothly. When the thumb is removed from the ear at the place desired, the rear end of the S-shaped plate spring engages with the teeth-shaped notches, by means of its flexibility, so that it may not back up by writing pressure. The lead being secured by the flexible plate spring, the writing touch of this mechanical pencil is good and comfortable.

Other objectives of the present invention will be apparent from the following detailed description of the preferred embodiment of the present invention taken in conjunction with the accompanying drawings.

In the drawings:

FIG. 1 is a side sectional view, partially exposed, of a mechanical pencil according to the present invention;

FIG. 2 is a sectional view, taken along line ll-ll on FIG. 1, as seen from the direction indicated by arrows;

FIG. 3 is an enlarged fragmentary perspective view, partially exposed, of the fore portions of the mechanical pencil shown in FIG. 1 and FIG. 2; and

FIG. 4 is an enlarged fragmentary perspective view, prior to assembly, of the fore end portions of the mechanical pencil according to another embodiment of the present invention.

In an embodiment shown in FIGS. 1, 2 and 3, the mechanical pencil includes an outer casing l in the same shape as a pencil. A conical tip portion of the outer casing l is provided with passage 3 through which a lead 2 is protruded. Within the fore portions of the outer casing I an inner casing 1', having almost half the length of the outer casing, is secured. The inner casing 1' includes a lower plane 4 arranged on the same level as a lower surface in the passage 3 and an upper plane 6 comprising a number of teeth-shaped continuous notches and opposing substantially parallel to the lower plane 4 to form a space 7 between them. An elongated split 12 communicating the exterior of the casing with the space is formed on the outer casing along the lengthwise direction thereof. A U-shaped (seen from top in FIG. 3) movable block l1 is loosely secured within the space 7 by means of a generally Sshaped plate spring 10. The rear end 8 of the S-shaped plate spring I0 is engaged with the teethshaped notches in its normal state. The fore end portion 9 of the spring 10 holds one end portion of the lead 2 and presses it down against the lower plane 4. An car 13, integral with the block 11, projects outside of the outer casing 1 through the split 12 and is movable along the split.

A stud l7, projecting from the fore portion of the lower plane 4, serves to unfasten the lead 2 from the binding pressure of the plate spring 10 when the fore end portion 9 of the S-shaped spring 10 is carried over the stud 17, thereby making the replacement of the lead easy and certain.

The rear portion of the outer casing 3 forms a housing 19 to reserve a supply of leads within it. A tail plug 18 is removably mounted to the rear end opening of the casing 1.

The ear 13 can be moved back and forth along the split 12 by the thumb of the hand holding this mechanical pencil in its writing position. ln operation, to advance the lead, an internal plane 15 of the movable block 11 pushes the plate spring 10. Then the rear end 8 of the flexible plate spring 10, engaging with the teeth-shaped notches 5, advances within the notches one by one, so that the lead 2 is protruded from the opening 3 as long as the notches continue. in operation, to back the lead, the lower edge of a rear plane 14 of the movable block ll pushes the curved rear portion 8 of the plate spring 10 and then presses it down so as to unfasten its engagement with the teeth-shaped notches, causing the plate spring E0 to be freely backed as it is pushed by a plane 16 of the block 11.

In the embodiment described above, although the outer casing l and the inner casing l are separately formed, modifications may be made. For example, two split outer casings may be made integral with two split inner casings, respectively, and bound together to form a unit casing.

in another embodiment as shown in H0. 4, a conical cap 20 is replaceably fitted to the fore end portion of the outer casing 1. When the cap 20 is removed, as shown in FIG. 4, the fore end portion 9 of the plate spring 10 is exposed when the car 13 is pushed to the foremost position and, therefore, the lead is replaceable without the stud 17 or anything equivalent to it. ln other respects, this embodiment is the same as the first embodiment.

Modifications may be made in the present invention within the scope of the subjoined claims.

lclaim:

l. A mechanical pencil comprising, in combination,

an elongated holder,

wherein the tip portion is provided with a lead protruding passage, the rear end portion is open and fitted with a tail plug, the interior of said holder includes a space formed between a lower plane on the same level as a bottom plane of the lead passage and a teeth-shaped plane arranged parallel to said lower plane, and the side surface of said holder has an elongated split communicating with said space, said split running along the holder;

a block slidable along said split and comprising an ear portion projecting outside of the split, said ear portion projecting about parallel with said planes forming said including at its fore end portion a stud serving to lift the fore portion of said plate spring in order to release the binding pressure of the plate spring on the lead. 2. A mechanical pencil as in claim I wherein the fore end portion of the holder is conical.

3. A mechanical pencil as defined in claim 1 wherein the rear portion of said elongated holder forms a housing for a supply ofleads. 

1. A mechanical pencil comprising, in combination, an elongated holder, wherein the tip portion is provided with a lead protruding passage, the rear end portion is open and fitted with a tail plug, the interior of said holder includes a space formed between a lower plane on the same level as a bottom plane of the lead passage and a teeth-shaped plane arranged parallel to said lower plane, and the side surface of said holder has an elongated split communicating with said space, said split running along the holder; a block slidable along said split and comprising an ear portion projecting outside of the split, said ear portion projecting about parallel with said planes forming said space, and a central portion formed integrally with said ear and positioned in said space, said central portion having an indentation so that it is U-shaped in plane view; and a substantially S-shaped plate spring, the rear end of said plate spring being engaged with said teeth-shaped plane, a portion of said plate spring being located within the said indentation in said block, and the fore end portion of said plate spring being adapted to hold an end of the lead by pressing it down against said lower plane, said lower plate including at its fore end portion a stud serving to lift the fore portion of said plate spring in order to release the binding pressure of the plate spring on the lead.
 2. A mechanical pencil as in claim 1 wherein the fore end portion of the holder is conical.
 3. A mechanical pencil as defined in claim 1 wherein the rear portion of said elongated holder forms a housing for a supply of leads. 